Hatsan 125 sniper spring replacement.

Hi, why do you want to replace your spring? Are your muzzle velocity numbers down/gun shooting wrong?

If you have to do it, I would suggest starting with a "how to build a spring compressor" video. You're gonna need one to safely disassemble your springer. Also I suspect that your end cap is very similar in shape to the one found on the Striker Edge/1000 models (stepped end cap). I had to fabricate a special tool to allow removal. Lastly, you have to figure out how to remove the safety. The auto safety lever can be a bit of a pain (again assuming that there are similarities between the Striker/1000 and 125 models). In closing: spring compressor, special tool, safety lever, and the rest should be just like any other spring gun seen on YouTube.